Current and Future Precipitation Extremes over Mississippi and Yangtze River Basins as Simulated in CMIP5 Models

Precipitation Extremes including both floods and droughts are major social and economic risks. The 1988 north-central U.S. drought and 1993 Great Midwest Flood caused over $60 and $18 billion loss respectively. The central U.S. experienced three 500-year floods in 15 years. Similarly extreme precipitation events in Yangtze River basin increasingly cause tremendous damages in China. Furthermore, observations show as climate changes continue to accelerate, the extreme precipitation become more extreme in most parts of the world. On regional scales, the characteristics and trends of precipitation extremes differ considerably (compared to temperature for example). This presentation contrasts two largest river basins in the Northern Hemisphere with similar geographic locations yet contrasting precipitation regimes: Mississippi River basin in the U.S. and Yangtze River basin in China over the central sections of two mid-latitude continents.

We first compare the observed precipitation extremes over the two basins, then examine the skills in capturing the observed extremes of 31 CMIP5 models in historical run that have saved daily output, and finally assess the projected future trends of extremes in the RCP8.5 run. Preliminary results show that 1) over China region the heavy precipitation events increased whereas light ones decreased during the second half of the 20th century, whereas over the U.S. region all categories of precipitation rate have increased in frequency, 2) most of 31 models have difficulty in reproducing the observed trends and spatial distribution of the extremes although they captured time-mean precipitation distribution reasonably well, and 3) summer precipitation is projected to decrease in the U.S. whereas it would increase in China, while winter precipitation would increase in both regions.